From: "Burakov, Anatoly" <anatoly.burakov@intel.com>
To: Olivier Matz <olivier.matz@6wind.com>,
dev@dpdk.org, "Ananyev,
Konstantin" <konstantin.ananyev@intel.com>,
"Richardson, Bruce" <bruce.richardson@intel.com>
Subject: Re: [dpdk-dev] [PATCH] ring: relax alignment constraint on ring structure
Date: Fri, 25 May 2018 15:57:07 +0100 [thread overview]
Message-ID: <5b5b3620-7674-86bb-125f-78e4796d2dea@intel.com> (raw)
In-Reply-To: <f9f02987-9fc5-c3ef-3a1d-c3229a408cd4@intel.com>
On 25-May-18 1:18 PM, Burakov, Anatoly wrote:
> On 25-May-18 11:59 AM, Burakov, Anatoly wrote:
>> On 03-Apr-18 2:26 PM, Olivier Matz wrote:
>>> The initial objective of
>>> commit d9f0d3a1ffd4 ("ring: remove split cacheline build setting")
>>> was to add an empty cache line betwee, the producer and consumer
>>> data (on platform with cache line size = 64B), preventing from
>>> having them on adjacent cache lines.
>>>
>>> Following discussion on the mailing list, it appears that this
>>> also imposes an alignment constraint that is not required.
>>>
>>> This patch removes the extra alignment constraint and adds the
>>> empty cache lines using padding fields in the structure. The
>>> size of rte_ring structure and the offset of the fields remain
>>> the same on platforms with cache line size = 64B:
>>>
>>> rte_ring = 384
>>> rte_ring.name = 0
>>> rte_ring.flags = 32
>>> rte_ring.memzone = 40
>>> rte_ring.size = 48
>>> rte_ring.mask = 52
>>> rte_ring.prod = 128
>>> rte_ring.cons = 256
>>>
>>> But it has an impact on platform where cache line size is 128B:
>>>
>>> rte_ring = 384 -> 768
>>> rte_ring.name = 0
>>> rte_ring.flags = 32
>>> rte_ring.memzone = 40
>>> rte_ring.size = 48
>>> rte_ring.mask = 52
>>> rte_ring.prod = 128 -> 256
>>> rte_ring.cons = 256 -> 512
>>>
>>> Link: http://dpdk.org/dev/patchwork/patch/25039/
>>> Suggested-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
>>> Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
>>> ---
>>
>> This patch causes eal_flags_autotest to hang on FreeBSD. Root cause at
>> this time is unknown, but this is a weird one - the test seems to hang
>> while doing read() in bsd/eal_thread.c:59. Reverting this patch on top
>> of rc5 results in eal_flags_autotest passing.
>>
>
> Further investigation shows that for some reason, if Enter is pressed
> while the test is seemingly "hung", it continues and passes. Or rather,
> it hangs on one test, and if Enter is pressed, it finishes that test and
> hangs on another, after which pressing Enter again will result in test
> succeeding. Weird...
>
This patch is OK, the problem is in the test :) With this patch, it
apparently blew up in just the right way, but really, the EAL flags
autotest is wrong on FreeBSD because it launches primary processes with
'--no-shconf' option, which corrupt main process's memory. For some
reason this only began manifesting with this patch.
--
Thanks,
Anatoly
next prev parent reply other threads:[~2018-05-25 14:57 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-30 14:26 [dpdk-dev] [RFC] " Olivier Matz
2017-07-20 8:52 ` Olivier Matz
2018-04-03 13:26 ` [dpdk-dev] [PATCH] " Olivier Matz
2018-04-03 15:07 ` Jerin Jacob
2018-04-03 15:25 ` Olivier Matz
2018-04-03 15:37 ` Jerin Jacob
2018-04-03 15:56 ` Olivier Matz
2018-04-03 16:42 ` Jerin Jacob
2018-04-04 23:38 ` Ananyev, Konstantin
2018-04-05 8:01 ` Jerin Jacob
2018-04-05 13:49 ` Ananyev, Konstantin
2018-04-06 1:26 ` Jerin Jacob
2018-04-11 0:33 ` Ananyev, Konstantin
2018-04-11 2:48 ` Jerin Jacob
2018-04-11 8:40 ` Ananyev, Konstantin
2018-04-17 22:15 ` Thomas Monjalon
2018-05-25 10:59 ` Burakov, Anatoly
2018-05-25 12:18 ` Burakov, Anatoly
2018-05-25 14:57 ` Burakov, Anatoly [this message]
2018-05-25 15:17 ` Olivier Matz
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